This invention relates to a vehicle dynamic control system which carries out warning and decelerating control in order to assist a vehicle in safely passing through a curve on a road in front of the vehicle.
Recently developed are several kinds of technology wherein road map data, provided from a navigator installed on a vehicle, are processed into road geometry data. Warning and decelerating controls are carried out after a judgement is made on the possibility of a vehicle passing through an approaching curve based on road data including the curvature of the curve and vehicle speed.
For example, Japanese Patent Laid-open No. 194886/1996 disclosed warning and vehicle speed control technology. Road data of a curve on a road are calculated based on road map data provided from a navigator. A permissible lateral acceleration allowable limit to enter into the curve and a foreseeable lateral acceleration at the entrance of the curve if the vehicle goes on at the present speed are calculated and compared. When the foreseeable lateral acceleration is larger than the permissible lateral acceleration, the present speed is judged as too high to enter into the curve, namely an over speed condition, and a warning and vehicle speed control are carried out.
When judging the possibility of passing through a curve, the approaching road to the curve is deemed to be a straight line and certain deceleration is applied to reduce an initial speed to a speed which is slow enough to allow the vehicle to safely pass through the curve.
Thinking about a case where the road to the objective curve is not a straight line, the judgement may not be made accurately by the calculation. In the case where the road is not a straight line, lateral acceleration occurs on the vehicle, resulting in forced reduction of deceleration based on a relation between longitudinal acceleration and lateral acceleration. Thus, an over speed judgement may be allowed by the system.
In order to eliminate the influence of the error, it may be a countermeasure to calculate permissible decelerations for all bends and then carry out the control. But as enormous calculations then would be required, processing speed becomes too slow for practical use.
The present invention provides a vehicle dynamic control system which can improve the accuracy of over speed judgement even in the case where a road leading to an objective curve is not a straight line, while minimizing the calculation load, during the process of making a judgement on whether present vehicle speed is an over speed or not after recognizing road geometry data of a curve on a road in front of the vehicle.
In order to achieve the aforementioned object, a vehicle dynamic control system according to the invention comprises a running condition detecting means for detecting running conditions of a vehicle, a road data detecting means for detecting road data of a road in front of the vehicle, a worth judging distance calculating means for calculating a worth judging distance from a point of operation to a curve on the road in front of the vehicle based on the road data, the worth judging distance being corrected and reduced according to curvatures of the road between the point of operation and the curve, a passing judgement means for judging the possibility of the vehicle passing through the curve based on the worth judging distance calculated by the worth judging distance calculating means, and a warning and deceleration control means for operating a warning means and activating at least one predetermined decelerating means according to the judgement of the passing judgement means.
In the vehicle dynamic control system according to the invention, the running condition detecting means detects vehicle running conditions, and the road data detecting means detects road data of the road in front of the vehicle. The worth judging distance calculating mean calculates the worth judging distance from the point of operation to the curve, correcting and reducing it according to curvatures of the road between the point of is operation and the curve. The passing judgement means judges the possibility of a vehicle passing through the curve according to the worth judging distance calculated by the worth judging distance calculating means. The warning and deceleration control means operates the warning means and activates at least one of the predetermined decelerating means according to the judgement.
The vehicle dynamic control system according to the invention may include a feature wherein the worth judging distance calculating means determines the worth judging distance, in terms of a permissible deceleration applicable at the winding part of the road in addition to the curvatures of the winding part of the road, the worth judging distance calculating means calculating the permissible deceleration by a friction circle relation between longitudinal and lateral accelerations. Thus, the concept of a friction circle is reflected in the control by the system so that precise control can be accomplished.
The vehicle dynamic control system according to the invention may further include a feature wherein the passing judgement means judges the possibility of a vehicle passing through the curve according to estimated running conditions based on running conditions at the point of operation and permissible running conditions based on running conditions for passing through the curve.
The vehicle dynamic control system according to the invention may further include features wherein the estimated running conditions include a standard deceleration applicable at the point of operation; the permissible running conditions include a permissible access speed for passing through the curve; the passing judgement means calculates a required deceleration to be applied until reaching the curve based on the permissible access speed, a vehicle speed at the point of operation and the worth judging distance; and the passing judgement means judges the possibility of passing through the curve by comparing the standard deceleration and the required deceleration in a predetermined manner. Namely, deceleration is a criterion for the judgement so that a precise control result can be obtained.